US Researchers Develop Method to Store Energy Using Sand

Researchers at the US National Renewable Energy Laboratory (NREL) developed a technology that uses sand to store energy. This method could offer a low-cost alternative to existing storage solutions and reduce the reliance on critical minerals like lithium. 

The patented technology is based on thermal energy storage (TES) and has been validated through a laboratory-scale prototype. It is estimated that a commercial-scale device could retain more than 95% of its heat for at least five days. The technology is based on heaters powered by renewable energy sources that can heat sand particles, which can be stored in silos to store the generated power. 

Jeffrey Gifford, Postdoctoral Researcher, NREL, emphasized the need for long-duration energy storage devices to achieve carbon reduction goals. He highlighted that this technology does not rely on rare earth metals or materials with complex supply chains, unlike lithium-ion batteries.
 

Zhiwen Ma, Head Researcher, NREL noted that sand is the cheapest option for energy storage compared to rival technologies such as compressed air energy storage (CAES), pumped hydropower, and batteries. Sand can store energy for hundreds of hours at a cost ranging from US$4 to US$10/Kwh.

CAES and pumped hydropower, for instance, can only store energy for tens of hours and come with higher costs/Kwh, from US$150 to US$300 for CAES and approximately US$60 for pumped hydropower. Lithium-ion batteries, while widely used, are limited to storing energy for one to four hours and cost around US$300/Kwh. Additionally, molten salts, another storage option, face limitations as they freeze at about 220°C and start to decompose at 600°C, making sand a more practical and cost-effective alternative for long-term energy storage needs.

The technology offers scalability by simply adding more sand, which incurs only in marginal costs. This scalability addresses a gap in current storage solutions, which struggle to provide cost-effective storage lasting from multiple hours to two weeks.

While the technology requires upfront costs for components to convert superheated sand back to electricity, the long-term savings are substantial. Craig Turchi, Researcher, NREL, noted that once these initial costs are covered, adding more sand for additional storage duration is much cheaper than adding more batteries.